Pitting corrosion of 12Kh18AG18Sh steel in chloride solutions

We experimentally established that the corrosion rate of 12Kh18AG18Sh steel in a 22% NaCl solution in the temperature range 20–100°C does not exceed 0.22 g/(m²·h) (or 0.277 mm/year). The material undergoes self-passivation with the formation of a protective passive film of Fe₃O₄+(Fe, Cr)₂O₃+(Mn, Fe)₂O₃. Pitting resistance of steel decreases in solutions with a concentration of chloride ions of above 0.2 mole/liter and temperatures of at least 40°C. We studied selective dissolution of certain components of steel and found that manganese is most soluble. Ionization of chromium occurs more slowly than that of the iron matrix. As a result of selective dissolution of steel, the passive film is depleted of manganese and nitrogen. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 3, pp. 81–85, May–June, 1999.